[backend]将testdata/下的测例替换为了赛方测试用例，更新了测试脚本

testdata/functional/22_if_test3.sy

@@ -0,0 +1,18 @@
+// test if-if-else
+int ififElse() {
+  int a;
+  a = 5;
+  int b;
+  b = 10;
+  if(a == 5)
+    if (b == 10) 
+      a = 25;
+    else 
+      a = a + 15;
+    
+  return (a);
+}
+
+int main(){
+  return (ififElse());
+}